Button die for dimpling



Feb- 22, 1955 c. c. HARRISON ET AL 2,702,577

BUTTON DIE FOR DIMPLING Filed April 30, 1951 W 2 nu n United StatesPatent O BUTTON DIE FOR DIMPLING Charles C. Harrison, Long Beach, BertB. Mead, Garden Grove, George D. Rechton, San Pedro, and Orville A.Wheelon, Pacific Palisades, Calif., assignors to Douglas AircraftCompany, Inc., Santa Monica, Calif.

Application April 30, 1951, Serial No. 223,804

7 Claims. (Cl. 153-21) This invention relates to hot dimpling ofrelatively hardalloy metallic sheets and particularly to means fordimpling such sheets while they are in place in their final assemblyposition on the basal framework of an airplane.

The airframe of most modern aircraft is constructed from prefabricatedpanels consisting of a metal frame covered-by a metal skin, usually ofan alloy of aluminum or magnesium. These panels are united to each otherand to the basal framework of the airplane by flush-riveting togetherand to the sub-adjacent framing overlappingly arranged marginal skinportions of adjacent panels, which operation usually completes theairframe. In effecting this union, the overlapping sheets are firstprovided with rivet holes in their marginal portions; thereafter the topor overlapping sheet has its edges raised and the rivet holes in theoverlapped sheet are dimpled with a male die while resting on the basalframe. Theoverlapping upper sheet is thereafter dimpled while raised.

Heretofore, dimpling this marginal edge of the overlapping sheetrequired the insertion of bre wedges between the sheets to space themfar enough apart to enable the insertion therebetween and around thepilot pin of the male die of a makeshift spacer in the form of a hardmetallic ring provided with a wire handle for positioning it. This ring,as conventionally used, has planeal upper and lower surfaces with sharp,hard peripheral edges.

During dimpling, a considerable amount of temporary upward overbendingof the upper, overlapping sheet in the region around the rivet hole isnecessary, the overbend absorbing dimplingstresses which would otherwisedistort the dimple and oilcan the sheet around the dimple. Since theupper surface of the conventional spacer ring is usually planeal, thesheet-contacting surface of the male die cannot be provided with a backangle to assist in overbending. Accordingly, this die has to be strokedhard in order to overbend the metal sufficiently around the rivet hole.The resultant high pressure forces the sharp upper and lower peripheraledges of the spacer ring into the pure metal cladding of the alloysheets and these edges often entirely abrade away the cladding. Thiscladding removal locally thins and weakens the sheets in the vitaljointures-regions of the air plane and also makes them quite subject tocorrosion. The unsightly appearance of such jointures adversely affectsthe opinion of inspectors as to the reliability of the workmanship ofthe fabricator. l

Again in dimpling the overlapping sheet heretofore, it was necessary toemploy a separate female die having an upper surface adapted tocooperate with the convexly conical part of the lower surface of themale die, the female die also having a lower surface adapted to fit inthe countersink drilled or teamed in the heavier overlapped sheetresting on the massive sub-structure. This separate die was interposedbetween the sheets concentrically inwardly of the spacer ring andsurrounding the pilot pin of the male die.

The present invention, in overcoming these and other defects, provides asingle piece, multi-function hand tool which is, in effect, a combinedfemale button type die for forming a dimple in the upraised sheet and aform block that enables the optimum temporary overbending of this sheetaround the holes therein without requiring high male die pressures. Ithence precludes the necessity for using separate spacer rings and femaledies and obviates exposure of the core of the sheets to corrosion.

In one of its now-preferred embodiments, the tool essentially consistsof an elongate, rectangular strip of metal of 2,702,577 Patented F eb.22, 1955 ICC low thermal conductivity. The one end of the strip isformed into a handle and the opposite end is formed into a female buttondie. The handle and the head are connected by a exible neck portionthinned in planform and in section or otherwise conformed to clear theoverlapping sheets and minimize heat transfer. The flexibility of theneck also facilitates placement of an aperture in the head between thesheets and around the pilot pin passing through both the aligned rivetholes therein. The peripheral lip of this aperture is downwardlyangularly deflected in such manner as to form a central conicalconcavity opening on the upper surface of the head and adapted tocooperate with the male die in dimpling and a central conical convexityon the lower surface of the head is concurrently thereby formed which isadapted to seat in the dimple preformed in the lower sheet or in thesubstructure. The upper surface of the head of the tool slopesdownwardly and outwardly away from the concavity therein at an angleequal to the back angle which the present invention makes it possible toemploy on the working face of the male die. The optimum overbending istherefore achieved in the upper sheet with a comparatively low male diepressure. Consequently, even if the peripheral edges of the head,contacting the upper and lower sheets, were sharp and hard, littlecladding would be removed thereby from either sheet. However, the broadsloping upper face terminates peripherally in round edges and the lowerdat face of the head is equally broad. Use of this tool thereforeeffects no removal of the cladding from either sheet.

This one of the presently preferred embodiments is illustrated in theaccompanying drawing and described hereinafter in conjunction therewithmerely in order Vto further clarify and sharply delineate the nature andsome of the advantages and practical aspects of the above and otherinventive concepts.

In the drawings:

Figure l is a top plan view of the tool;

Figure 2 is a perspective view thereof partly in section;

Figure 3 is a side elevational view of the tool; and

l Figure 4 is a longitudinal section of the tool in use in s1tu.

The drawing shows the tool as a generally rectangular elongate strip oftempered stainless steel 1l) terminating at the one end in a handle 11and at the opposite end in a head 12. The handle may be shaped to litcomfortably in the hand of the operator and the head is preferablycircular and includes formations adapting it to act as a combined sheetspacer and overbender, and as a female, button-type dimpling die.

The head and the handle are joined by a neck portion 13 which isconstricted in plan-form and thinned in the direction at right anglesthereto, or thicknesswise, thereby to render the tool somewhat flexiblelongitudinally. By means of the handle and the flexible neck, anaperture 1.4 in the head can be readily inserted between the wedgespacedsheets 15 and 16 and flexibly fitted around the pilot pin 17 of theheated male dimpling die 18, which pin passes through the aligned rivetholes 19 and 20 of the overlapped sheets 15 and 16. Thereafter, thewedges are withdrawn and this tool acts as the sole sheet spacing means.The periphery of the rivet hole 20 has already been countersunk as at 21in conformity with an aperture 22 in the relatively massivesub-structure 23, and the peripheral lip of the aperture 19 is to bedimpled in conformity with the countersink 21.

The neck portion 13 extends from the outermostperiphery of the head tothe innermost portion of the handle, and since it clears both sheets andmay have any desired linear extent, on occasion occupying most of thelength of the tool, it can be so made as to reduce that area of the toolthat makes heat transferring contact with the sheets, to the minimum.Thereby, loss of dimpling heat from the male die and the lip of therivet hole 19 is minimized so that there is little danger of the lipcooling to such an extent as to crack when the male die is stroked.

The head of the tool is preferably swaged or otherwise thickened to athicknesswise dimension greater than that of the handle, in order tofacilitate sheet-overbending and, being composed of a metal having arelatively low thermal conductivity such as stainless steel, minimizesheat loss fromthe lip of the upper dimple to the sub-structure. Thisfact, combined with the structure of the neck, effectively prevents thelip in the upper sheet from cooling off to an extent sufficient toinduce radial or circumferential cracks in the dimple when the male dieis stroked.

The flexible neck enables the head to absorb the heaviest type of diestroke without damage to the head, since this neck permits the head tobodily yield downwardly .and inwardly to an extent that preventsfracture of the head.

The invention contemplates that the specific shape of the die in thehead, and of the head itself, can be readily altered to suit varyingconditions without departing from the scope of the present concepts.

The upper peripheral edge of the aperture 14- in the head of the tool issurrounded by a concavity 24 which is downwardly angularly deflected toa degree conforming to the downward angular formation of the countersink21 in the heavier lower sheet, in order to enable nesting of the twoformations in the sheets when they are riveted. This downward deflectionforms, in the central region of the lower face of the head of the tool aconically convex formation 25 which centers and seats the head in thecountersink in the sheet 16. The lower circular surface of the head,lying radially outwardly of the convexity 25, is flat and planeal and isadapted to fayingly contact the upper surface of the sheet 16 over arelatively large area as compared to the previously employedbushing-type spacer rings. Consequently, the pressure of the male die isdistributed over an enlarged area and the die loading of the sheets perunit of area thereof is reduced considerably.

The central portion of the upper face of the head, rendered concave asat 24, as a consequence of the downward deflection of the lips of theaperture 14, is angled to the degree properly to dimple the lip of therivet hole in the upper sheet. This degree may vary with the type ofdimple desired. The upper face 26 of the head, beginning at theperiphery of the concavity, is outwardly and downwardly angled, in itsentire circumferential extent, at a predetermined angle to the planeallower face. This angle is usually of the order of 3 and corresponds tothe back angle or upwardly reentrant angle, on the working face 29 ofrthe male die. The peripheral edge of the head, on both the upper andthe lower faces thereof, may be rounded to further diminish the chancesof marring the sheets.

By Virtue of the back angle surface 26 on the upper face of the headenabling the employment of an equal back angled surface 29 on theworking face of the male die,

.a lower pressure in stroking the male die is required to overbend thesheets around the rivet holes than when the bushing type spacer rings ofthe prior art are employed. Consequently, the pressural reaction of thehead on the sheets contacting it is considerably reduced withoutreducing the overbend. Marring of the cladding o n the sheets is therebyreduced to the minimum.

It will be understood that the same dimpling operation can be performedon a sheet immediately overlying a framing structure in which acountersink has been preformed.

Although one of the now-preferred embodiments of the invention has beendescribed in most of its speciiic details, it is to be understood thatthe description has been given only by way of example of the many formswhich the invention may take. The invention itself is not in any wiselimited to these or other specific structural details except asnecessitated by the scope of the annexed claims.

We claim:

l. A hand-held, spoon-type button die adapted to cooperate in situ on aframed and plated structure with a male die having a pilot pin so as todimple a rivet hole in the one of a pair of overlapping sheets which areseparable transversely of the overlapping portions to provide a limitedspace transversely of the overlapping portions, said sheets being tixedto a perforate substructure, the other sheet having a countersunk rivethole therein registerable with the iirst said rivet hole, comprising: anelongate strip of material having a button-type head at the one endportion thereof, substantially all of the strip except said head portionconstituting a handle, said button-type head being no thicker than thelimited distance renderable available between the two overlapping sheetsto be dimpled; a bore extending transversely fully through said head,said bore being arranged and adapted to receive therethrough the pilotpin on a cooperative male dimpling die; a concavity arranged on the onesurface of said head and lying concentrically with said bore for deninga .female die; .a convexity arranged on the opposite surface of saidhead and lying concentrically with said bore so as to dually definesubstantially a male die and an anchor for anchoring said head in saidcountersink between said sheets; a planeal, smooth surface annularlyconcentrically surrounding said concavity and sloping downwardly andoutwardly therefrom at an angle sufficient to enable the stressabsorbingover-bending of the first said sheet thereon by said male die, saidplaneal smooth surface having an area suicient to prevent ringing of theportions of said sheet contacted by said male die and by said planealsmooth surface and having chamfered peripheries; and a planeal, smoothannular surface extending radially outwardly on said opposite face fromsaid convexity in substantial parallelism to the handle of said tool andhaving an area adapted to congruently lit the adjacent surface of thesecond-said sheet so as to prevent ringing of said sheet under the maledie-stroke.

2. A tool adapted for use in situ on a plated structure with a male diehaving a pilot pin so as to enable dimpling a hole in the one of a pairof overlapping perforate sheets which form part of the plating andoverlie a perforation in a substructure the other of said sheetsincluding a countersunk rivet hole therein arranged in coaxial alignmentwith the lirst-said hole and adapted to receive the dimple, .theoverlapping sheet-portions being temporarily separable in the directionextending transversely thereof to provide a space extending transverselyof the overlapping portions, comprising: an elongate strip of materialhaving a head at the one end portion of the strip, the dimension of saidhead thicknesswise of the strip being no greater than the transverselyextending space render-able available between said overlapping portions;substantially all the strip, excepting said head, constituting a handle;a bore lying thicknesswise of said head and extending entirely throughsaid head; said bore defining means for receiving entirely through saidhead the pilot pin of a male dimpling die so as to enable the pilot pinon the male die to enter the perforation in the substructure and anchorthe perforations in said sheets, head and substructure in mutual coaxialregistry with each other and with the male die during stroking of themale die, thereby to preclude cooking of the dimple relatively to theaxis of the hole in the firstsaid sheet; and a concave surface arrangedon the one face of said head transversely of and coaxially with the oneend of the aforesaid receiving bore and adapted to constrain theperipheral margin of the hole in the first-said sheet to conform to apredetermined dimple shape.

3. A tool adapted for use in situ on a plated structure with a male diehaving a pilot pin so as to enable dimpling a hole in the one of'a pairof overlapping perforate sheets which form part of the plating andoverlie a perforation 1n a substructure, the overlapping sheet-portionsbeing temporarily separable in the direction extending transverselythereof to provide a space extending transversely of the overlappingportions, comprising: an elongate strip of material having a head at theone end portion of the strip, the dimension of said head thicknesswiseof the strip being no greater than the transversely extending spacerenderable available between said overlapping portions; substantiallyall the strip, excepting said head, constituting a handle; a bore lyingthicknesswise of said head and extending entirely through said head;said bore delining means for receiving entirely through said head thepilot pin of a male dimpling die so as to enable the pilot pin on themale die to enter the perforation in the substructure and anchor theperforations in said sheets, head and substructure in mutual coaxialregistry with each other and with the male die during stroking of themale die, thereby to preclude cooking of the dimple relatively to theaxis of the hole in the first-said sheet; a concave surface arranged onthe one face of said head transversely of and coaxially with the one endof the aforesaid receiving bore and adapted to constrain the peripheralmargin of the hole in the first-said sheet to conform to a predeterminedshape; and a convex surface arranged on the opposite face of said headtransversely of and coaxially with the opposite end of the above saidreceiving bore, said convex surface seating in a countersink disposedcoaxially on the adacent end of the perforation in the second-said sheetand adapted to anchor said head and said concave surface in coaxialitywith all the aforesaid holes in the absence of said pilot pin thereinand before the male die descends.

4. A tool adapted for use in situ on a framed and plated structure, inassociation with a male die of the type having a pilot pin, so as todimple a perforation in the one of a pair of overlapping sheets formingpart of the plating, the overlapping portions of said sheets beingtemporarily separable transversely thereof to provide a space extendingtransversely of, and between, said overlapping portions, the other sheetof said pair including a countersunk perforation therein deviating froma predetermined, standard shape and adapted to be reformed to saidpredetermined shape, comprising: an elongate strip of material having ahead at the one end portion thereof, substantially all the strip, exceptthe head-portion, constituting a handle; said head having athicknesswise dimension no greater than the limited space renderableavailable transversely between the overlapping portions of said sheet byurging said portions relatively oppositely; a bore extendingthicknesswise of said head and penetrating entirely through said head,said bore being arranged and adapted to receive therethrough the pilotpin on a male dimpling die so as to enable the pin to pass through saidsheets and said head and center a perforation in a substructure; aconcave, frustoconical surface arranged on the one face of said head andlying transversely of, and coaxially with, the one end of said receivingbore; and a convex frustoconical portion of said head arranged on theopposite face of said head and lying transversely of, and coaxiallywith, the opposite end of the receiving bore, said convex portion havinga predetermined shape corresponding to the aforesaid desiredpredetermined shape of said countersink, and being adapted to forminglyt in said countersink so as to reform said countersink to said desiredshape upon application of a coaxial stroking force to said headsubstantially concurrently With the dimpling of the perforation in therst-said sheet.

5. A spoon-type dimpling tool for use in dimpling a rivet hole in theone of a pair of overlapping sheets, the other of said sheets having acountersunk rivet hole therein for receiving the protruding portion ofthe dimple, comprising: a strip of material having a thin head portionforming a button-die; a bore extending transversely through saidbutton-die for receiving therethrough the pilot-pin on a cooperatingmale die; a concavity arranged on the one surface of said dieconcentrically with said bore so as to dene female dimpling means; aconvexity arranged on the opposite surface of said die concentricallywith said bore so as to dene male dimpling means; and a frusto-conicaloverbending surface arranged concentrically with said concavity andlying on the same surface of said die therewith and extending laterallyoutwardly from said concavity; said frusto-conical surface being smoothand having a total area suiciently large to minimize the unitoverbending stress on the first-said sheet during dimpling so as toinhibit ringing of the iirst-said sheet by the spoon-type tool.

6. A spoon type dimpling tool for use in dimpling a rivet hole in theone of a pair of overlapping sheets, the other of said sheets includinga countersunk rivet hole therein arranged in coaxial alignment with thefirst-said hole and adapted to receive the dimple, comprising: a stripof material having a thin head portion forming a button-die; a boreextending transversely through said head portion for receiving a pilotpin; a dimple-forming concavity arranged on the lirst face of saidhead-portion concentrically with said bore; a convexity arranged on thesecond of said head-portion concentrically with said bore; and a planealsurface disposed concentrically of said bore around said convexity atright angles to said bore and extending laterally outwardly from thebase of said convexity; said planeal surface being adapted to contactthe subadjacent face of said second sheet, and said planeal surfacebeing smooth and having an area suciently large to minimize theunit-load on said sub-adjacent surface; thereby to prevent ringing ofsaid sub-adjacent surface.

7. A spoon type dimpling tool for dimpling a rivet hole in the one of apair of overlapping sheets, the other of said sheets including adeformed or out-of-round countersunk rivet hole arranged in coaxialalignment with the first-said hole and adapted to receive the dimple,comprising: a strip of material having a thin head portion forming abutton-die; a bore extending transversely through said head portion forreceiving a pilot pin; a dirnple-forming concavity arranged on the firstface of said head-portion concentrically with said bore; a convexityarranged on the second of said head-portion concentrically with saidbore; said convexity having an exterior surface preshaped to the desiredform for the countersunk portion of said rivet hole, said exteriorsurface being adapted to be forcefully urged formingly into saidcountersunk portion so as to reform the latter to said desired shape.

References Cited in the le of this patent UNITED STATES PATENTS 556,060Pierre Mar. 10, 1896 2,288,378 Veit lune 30, 1942 2,292,446 Huck Aug.l1, 1942 2,491,717 Creighton Dec. 20, 1949 2,508,373 Cavallin May 23,1950

